1. Field of Invention
This invention relates to actuators. Specifically, the present invention relates to devices and components thereof for selectively initiating an action and further relates to methods for making such devices and components.
2. Description of the Related Art
Initiators are employed in various demanding applications, including airbag activation, munitions detonation, solid rocket motor ignition, aircraft pilot ejection, and so on. Such applications often require relatively safe initiators that do not activate unless a predetermined set of conditions are met.
Safe initiators are particularly important in munitions applications, where inadvertent activation of an explosive charge can be devastating. For the purposes of the present discussion, an initiator may be any device or module that initiates or starts an action in response to a predetermined signal or sensed condition. An actuator may be anything that causes or performs an action when activated. Munitions that are equipped with relatively safe initiators are often called insensitive munitions. Ideally, insensitive munitions will not explode, even in a fire, unless desired conditions are met.
Insensitive munitions are often equipped with Exploding Foil Initiators (EFIs). An example EFI includes a silicon substrate with an exploding foil, often called a bridge, coupled between two electrodes, called lands. A flyer is positioned on the bridge and near an explosive charge. A barrel may act as a spacer between the foil and the explosive charge. A fireset is coupled to the electrodes. When certain desired conditions are met, the fireset applies a high voltage pulse to the electrodes sufficient to explode the foil. The exploding foil propels the flyer into the explosive charge at sufficiently high velocities to detonate the explosive charge.
Unfortunately, conventional EFIs are often bulky, inefficient, and expensive. Certain EFI design constraints may necessitate individually constructed EFIs with hand-placed or machine-placed components, such as flyers, barrels, and electrodes that electrically couple the firesets to the bridges. Such manually placed discrete components are prone to misalignment relative to the foil and may dislodge or move over time, which reduces EFI efficiency, reliability, and longevity. For example, a misplaced flyer and barrel may result in a misguided flyer that reduces the effectiveness of the flyer in detonating the explosive charge.
Existing EFI construction techniques may necessitate relatively large EFIs to facilitate manual flyer and barrel placement and to mitigate inaccuracies in flyer and barrel placement. Complicated and expensive machines and processes may be required to accurately position discrete EFI components. In addition, discretely placed components are often prone to undesirable movement or displacement in response to shock or vibration, which may occur, for example, during missile flight. Furthermore, the EFIs may require excessively large and expensive firesets to produce sufficient voltage and flyer velocity to compensate for inaccuracies in EFI-component placement and design inefficiencies.
Attempts to improve EFI performance include use of a ring-shaped bridge for blasting a flyer out of a layer of flyer material, as discussed in U.S. Pat. No. 6,234,081, entitled SHAPED BRIDGE SLAPPER. Unfortunately, such EFIs generally still require manual or machine placement of discrete components, resulting in expensive and error-prone EFIs.
Hence, a need exists in the art for a compact high performance EFI and an accompanying reliable, cost-effective, and efficient process for making the EFI.